thp/doc-generator/markdown/en/docs/latest/functions/definition.md

Function definition

Functions are defined with fun followed by the name of the function, the parameters, the return type, = and an expression.

Function with no parameters

To declare a function with no parameters include (), and call it with ().

fun getName() =
    // code...

val name = getName()

Function that returns void/nothing

In Misti we return Unit instead of void, null, undefined or others.

So a function that doesn't return anything, would return Unit.

// This function just prints Hello and returns
fun printHello() -> Unit =
    print("Hello")

This type, Unit, is treated like void, so it is ignored.

If a function doesn't return anything, Unit can be omitted.

// This first declaration
fun doSomething() -> Unit =
    something()


// is equivalent to this one
fun doSomething() =
    something()

Function with return

First, the return type must be defined in the declaration.

Let's say that a function getLuckyNumber returns a Float, then it would be declared like this:

fun getLuckyNumber() -> Float =
    // Body of the function

And finally, the return value is the last expression in the function. The following function will return 7.

fun getLuckyNumber() -> Float =
    // This '7' is the last expression, so it will be returned
    7


val number = getLuckyNumber()  // number = 7

Return multiple values

We can use a tuple if we need to return multiple values.

fun getPerson() -> #(Str, Int) =
    // Logic...
    #("Kim", 33)


fun tupleContains(#(Str, Int) data, Str key) -> #(Bool, Int) =
    val #(currentKey, value) = data
    if currentKey == key do
        #(true, value)
    else
        #(false, 0)


tupleContains(#("Test", 200), "Test")